The present invention relates to an improved breather valve that controls the internal pressure of a sealed container, such as a fuel tank, by opening or closing a valve element in response to the change of the internal pressure.
The internal pressure of sealed containers, such as fuel tanks for motorcycles and outboard motors, are subject to changes due to fuel comsumption, increase of fuel vapor partial pressure caused by a temperature change, and so forth. Conventionally, various types of breather valves have been proposed to prevent damages caused by such changes of the internal pressure of sealed containers. Japan Published Unexamined Utility Model Application 61-108573 disclosed such a breather valve, in which the inside of the container is connected to the atmosphere via a small bore.
Japan Published Examined Utility Model Application 60-34850 discloses a pressure control valve which prevents gasoline vapor from escaping from a fuel tank into the atmosphere. More specifically, the apparatus includes a breather valve and a breather passage which connects a fuel tank with an absorption unit filled with activated carbon for absorbing gasoline vapor. A negative pressure inside the fuel tank moves the breather valve against the pressure of a spring to connect the fuel tank with the absorption unit and allow air to go into the fuel tank. On the other hand, high pressure inside the fuel tank causes a diaphragm to move against the pressure of another spring. This causes a lever to push onto and detach the valve from a shoulder, thus exhausting the gasoline vapor from the fuel tank to the absorption unit.
These conventional breather valves generally require a complex structure with many components, including a plural springs, a diaphragm, a valve element, and a lever. The diaphragm especially tends to make such a breather valve large in size and thus make it difficult to install the valve in a motorcycle or an outboard motor.